When a thin film of saliva covers the enamel surface, strong specular reflection (glare) occurs. This glare prevents optical sensors from accurately capturing surface topography. Polarization technology is one of the core solutions to this problem.
Principle of Polarized Light
Light is a transverse wave whose vibration direction is perpendicular to its direction of propagation. Natural light vibrates uniformly in all directions, while specular reflected light (glare) tends to become polarized in a specific direction. Polarization technology exploits this difference to separate useful signal light from noise light.
Implementation in Intraoral Scanners
A polarizer (linear polarizing filter) is placed in front of the light source so that the light projected onto the tooth surface becomes linearly polarized.
Specular reflection from the enamel surface preserves the original polarization direction, while diffuse reflection that scatters inside the tooth becomes randomly polarized.
An analyzer is mounted in front of the sensor with its polarization axis oriented orthogonally (perpendicular) to the polarizer.
Specular reflected light is blocked by the crossed analyzer because its polarization direction remains unchanged. Randomly polarized diffuse light partially passes through.
As a result, the sensor primarily receives diffuse light that carries surface topography information, effectively filtering out glare.
3Shape's Polarization Approach
The 3Shape TRIOS series is a well-known example of polarization-based intraoral scanning. Polarization technology helps compensate for the translucency and high reflectivity of enamel and is one of the key enablers of its powder-free scanning capability.
Limitations of Polarization Technology
Polarizing filters reduce light intensity, requiring a stronger light source to compensate.
Metal surfaces behave differently; polarization filtering is less effective on metals. Scan bodies and amalgam restorations may still require special handling.
Polarizing filters can age under repeated high-temperature and high-pressure sterilization, potentially reducing filtering performance.
Alternative Approaches Used by Other Brands
Multi-spectral imaging leverages differences in reflection characteristics across wavelengths.
AI algorithms identify and remove glare regions during post-processing.
Some systems recommend applying a matte spray to highly reflective metal surfaces.
Understanding polarization technology clarifies why powder-free scanning is possible on enamel yet more challenging on metals, and why sensor design, light management, and software algorithms must work together for reliable clinical results.
At Aident Technology, the AI-30 intraoral scanner series prioritizes robust optical performance and real-time processing to deliver clear, high-accuracy digital impressions. With ≥30 fps capture, ≤10 μm accuracy, powder-free true-color scanning, and intelligent anti-fog heating, the AI-30 is engineered for consistent results across varied clinical surfaces.
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